“两硬”条件下冲击地压微震信号特征及前兆识别

Features of microseismic events and precursors of rock burst in underground coal mining with hard roof

结合微震监测数据,对大同忻州窑矿8935"两硬"条件工作面回采过程中发生的冲击现象进行分析;从微震事件震源定位、能级与频次关系以及冲击前微震信号频谱演化规律等方面讨论了该工作面冲击地压机理及前兆信息特征。研究表明:8935工作面冲击地压为坚硬顶板破断诱发煤柱区域积聚能量的突然释放所致;冲击震源多在工作面超前50 m范围内沿采空区煤柱侧,且主要集中在坚硬顶板断裂后发生压缩、反弹的空间区域;冲击地压前微震事件频次、能量、微震信号b值及主频均呈下降趋势。冲击地压前微震频谱主要集中在5-60 Hz,微震主频急剧降低和幅值明显升高可视为冲击前兆特征之一。

The characteristics of rock burst were analyzed based on the microseismic data from No.8935 working face in Xinzhouyao Coal Mine,Datong Mining Group.The geology of this working face was characterized by the thick sandstone roof and coal seam,both with relative higher stiffness and strength.In order to investigate the mechanism and precursors of rock burst occurred in No.8935 working face,the locations of microseismic,the relationship of microseismic energy and frequency and the spectrum of microseismic signals were analyzed.The results show that the rock burst in No.8935 working face are mainly induced by the seismic caused by roof failure.The coal pillar near the goaf is more easily to bump.The statistics results indicate that the rock burst are mainly occurred in the gate road near the pillar,less than 50 m ahead of working face and located in the hard roof adjacent with coal seam.Moreover,the frequency,energy,b-value and frequency spectrogram of microseismic events are found to decrease before rock burst.It was found that the frequencies of the microseismic events before rock burst mainly concentrates upon 5-60 Hz.The sudden decreasing of frequency and increasing of amplitude of microseismic events can be regarded as a precursor of rock burst.